Polymers for absorbing water or aqueous solutions are used in numerous commercial and industrial applications. For example, polymers are used to improve water absorbency of paper towels and disposable diapers.
Though known water absorbing polymers are highly absorbent to deionized water, they are dramatically less absorbent to aqueous solutions such as salt water, brine, and urine. For example, hydrolyzed crosslinked polyacrylamide absorbs 1,024 grams of deionized water per gram of polymer, but only 25 grams of synthetic urine per gram of polymer. Crosslinked polyacrylate absorbs 423 grams of deionized water per gram of polymer, but only 10 grams of synthetic urine per gram of polymer. Hydrolyzed crosslinked polyacrylonitrile absorbs 352 grams of deionized water per gram of polymer, but only 25 grams of synthetic urine per gram of polymer. Analogous starch-grafted copolymers generally have very poor absorbency to synthetic urine.
It would be a valuable contribution to the art to develop polymers with high absorbency to not only water but also aqueous solutions. The market for these types of copolymers is large and the uses are numerous. Therefore, seemingly small improvements in the absorbency translate into large savings in the quantity of polymer required to absorb these liquids and large savings to consumers.